Cornelius,
you cant buy large diameter round aluminum tubing,you need to get 3/8" sheet,have it cut,then rolled then tig welded, it all has to be custom fit to the boat,i assume this 65 foot boat is in the water,so that means a diver will have to go in the water to take measurements off the prop,shaft,rudders,plus fittings will have to be installed in the hull under the boat as well as on the stern,not a easy job while working under water,plus if they decide to have the boat hauled out,that would cost them over 1000 bux,then you have boat storage for the lenth of the time it takes to have the blower custom made and fitted to the boat,plus they may want to scrape and repaint the hull while its out of the water,more time,you have labor too,plus travel time,lots of fuel,an gas isnt cheap these days.in about a month i have to drive 4 hours to the keys to HRD's boat,thier blower is sitting on the bottom of the canal where thier boat is moored,the brackets that held it on snapped (poor welding,i didnt build thier blower)the last time we were out on one of the 1733 fleet wrecks,i have to float it to the surface,tow it across a canal,have a crane lift it out of the water into my truck,bring it back to my shop an weld new brackets on it,then take it back down there have the crane lower it to the stern use the winch on the boat with the help of 4-5 people an install it back on the boat
